This invention is a device for displaying information from a microdisplay in an enlarged format. It is recognized that microdisplays can be used in hand-held devices such as pagers, video and digital cameras, cellular telephones, and card readers. The user holds the system in proximity to their eye such that they view the microdisplay through an optical system which magnifies the image on the microdisplay. Small area displays can be made using different technologies including transmission or reflective liquid crystal displays, light emitting diode (LED) array displays, electroluminescent displays, digital micro-mirror displays and field emission displays.
It is a desire to have an image which is viewable by a user at a distance greater than a few inches from the device containing an electronic display. The present invention produces a magnified image from a small area display that is directed along an optical path to viewing surface optical elements readable at a greater distance.
A preferred embodiment of the invention relates to a microdisplay viewer having an electronic display and an optical system that enlarges the image for viewing within an arm""s length of the user, for example. A lens enlarges the image produced on the microdisplay. A mirror reflects the enlarged image from the lens. In a preferred embodiment, the display is an active matrix liquid crystal display with an array of at least 75,000 pixel electrodes and an active area of less than 400 mm2. A light source illuminates the array of pixel electrodes.
The hand-held microdisplay unit, in a preferred embodiment, has a curved mirror and a display device having a lens system positioned between the mirror and the display. The curved mirror can be a concave mirror, preferably a spherical mirror, that reflects the light from the lens system and directs the image along a viewing axis.
The viewer in another preferred embodiment has a planar mirror and a viewing screen. In a preferred embodiment, the screen is a Fresnel lens. The lens allows redirection of light to the user""s eye. The viewing screen can have a diffuser and a Fresnel lens, for example, through which the image is viewed. The image of the microdisplay is projected through the lens system to the mirror and to the viewing screen.
In a preferred embodiment, a light pipe is interposed between the light source and the liquid crystal display for compressing the light from the light source to fill the liquid crystal display and increasing uniformity of the light. The light source is at least one light emitting diode. A condenser lens is interposed between the light pipe and the liquid crystal display for maximizing collection of the light into the display.
A preferred embodiment of the viewer can include a mechanical assembly that can be manually actuated between a xe2x80x9cclosedxe2x80x9d or storage position and an xe2x80x9copenxe2x80x9d or operating position. In the storage position, the display image cannot be seen by the user, however, the viewer is in a more compact state, occupying less than 600 cm3, providing for ease of transport or storage. In the operating position, the viewer housing is opened to provide the enlarged optical path needed for viewing the enlarged image from the display.
The active matrix display can be a transmissive or reflective liquid crystal display, or other electronic display having a small area and sufficient resolution.